1. Field of the Invention
The present invention relates to optical signal processing apparatus and more particularly to an optical apparatus having a mirror array.
2. Background of the Related Art
Electro-optic devices often employ an array of micro-machined mirrors, each mirror being individually movable in response to an electrical signal. For example, the mirrors can each be cantilevered and moved by an electrostatic force. Typically, electro-optic mirror array devices can be used as optical cross connects in optical communication systems, visual presentations and displays, for example. Generally, each mirror of the cross connect is addressed by a number of electrical lead lines and receives a beam of light from, for example, an individual optical fiber in a fiber optic bundle. The beams reflected from the mirrors are individually directed to a prespecified location (for example, another fiber optic bundle) by individually moving the mirrors.
It is desirable to have a high density of optical transfer. However, large mirror arrays are generally not feasible because the electrical interconnection density often presents a bottleneck. As the number of mirrors in an array increases, the number of electrical lead lines also increases, and these lead lines must be crowded into more confined spaces. For example, a 256 mirror array chip (16.times.16 array) with four lead lines per mirror requires 1,032 wirebond pads and electrical interconnections. The electrical leads must be adequately spaced to handle relatively high voltage (e.g., 100-150 volts). Hence there is a limit as to how small the leads can be made and how closely they can be spaced apart from each other. The routing of this number of electrical wires between the individual mirror elements, and routing from the chip center to the outer edge, forces the mirror spacing to be larger than desired and limits the useful size of the integrated array.
What is needed is an electro-optic chip which includes a larger array of mirrors while not increasing the mirror spacing.